Alien Swarm Parasite
General

The Parasite hat came at the 20th of July 2010 with a TF2 Patch to celebrate the release of Alien Swarm (http://www.alienswarm.com/). The Alien Swarm Parasite is an unlockable headwear item for all Classes. It is obtained by earning the Hat Trick achievement in the game Alien Swarm by completing 2 co-op missions online.